6.7
Table Of Contents
- vSphere Availability
- Contents
- About vSphere Availability
- Business Continuity and Minimizing Downtime
- Creating and Using vSphere HA Clusters
- Providing Fault Tolerance for Virtual Machines
- How Fault Tolerance Works
- Fault Tolerance Use Cases
- Fault Tolerance Requirements, Limits, and Licensing
- Fault Tolerance Interoperability
- Preparing Your Cluster and Hosts for Fault Tolerance
- Using Fault Tolerance
- Best Practices for Fault Tolerance
- Legacy Fault Tolerance
- Troubleshooting Fault Tolerant Virtual Machines
- Hardware Virtualization Not Enabled
- Compatible Hosts Not Available for Secondary VM
- Secondary VM on Overcommitted Host Degrades Performance of Primary VM
- Increased Network Latency Observed in FT Virtual Machines
- Some Hosts Are Overloaded with FT Virtual Machines
- Losing Access to FT Metadata Datastore
- Turning On vSphere FT for Powered-On VM Fails
- FT Virtual Machines not Placed or Evacuated by vSphere DRS
- Fault Tolerant Virtual Machine Failovers
- vCenter High Availability
- Plan the vCenter HA Deployment
- Configure the Network
- Configure vCenter HA With the Basic Option
- Configure vCenter HA With the Advanced Option
- Manage the vCenter HA Configuration
- Set Up SNMP Traps
- Set Up Your Environment to Use Custom Certificates
- Manage vCenter HA SSH Keys
- Initiate a vCenter HA Failover
- Edit the vCenter HA Cluster Configuration
- Perform Backup and Restore Operations
- Remove a vCenter HA Configuration
- Reboot All vCenter HA Nodes
- Change the Appliance Environment
- Collecting Support Bundles for a vCenter HA Node
- Troubleshoot Your vCenter HA Environment
- Patching a vCenter High Availability Environment
- Using Microsoft Clustering Service for vCenter Server on Windows High Availability
4 Determines whether the Current Failover Capacity is less than the Configured Failover Capacity
(provided by the user).
If it is, admission control disallows the operation.
Note You can set a specific slot size for both CPU and memory in the admission control section of the
vSphere HA settings in the vSphere Client.
Slot Size Calculation
vSphere HA Slot Size and Admission Control
(http://link.brightcove.com/services/player/bcpid2296383276001?
bctid=ref:video_vsphere_slot_admission_control)
Slot size is comprised of two components, CPU and memory.
n
vSphere HA calculates the CPU component by obtaining the CPU reservation of each powered-on
virtual machine and selecting the largest value. If you have not specified a CPU reservation for a
virtual machine, it is assigned a default value of 32MHz. You can change this value by using the
das.vmcpuminmhz advanced option.)
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vSphere HA calculates the memory component by obtaining the memory reservation, plus memory
overhead, of each powered-on virtual machine and selecting the largest value. There is no default
value for the memory reservation.
If your cluster contains any virtual machines that have much larger reservations than the others, they will
distort slot size calculation. To avoid this, you can specify an upper bound for the CPU or memory
component of the slot size by using the das.slotcpuinmhz or das.slotmeminmb advanced options,
respectively. See vSphere HA Advanced Options.
You can also determine the risk of resource fragmentation in your cluster by viewing the number of virtual
machines that require multiple slots. This can be calculated in the admission control section of the
vSphere HA settings in the vSphere Client. Virtual machines might require multiple slots if you have
specified a fixed slot size or a maximum slot size using advanced options.
Using Slots to Compute the Current Failover Capacity
After the slot size is calculated, vSphere HA determines each host's CPU and memory resources that are
available for virtual machines. These amounts are those contained in the host's root resource pool, not
the total physical resources of the host. The resource data for a host that is used by vSphere HA can be
found on the host's Summary tab on the vSphere Client. If all hosts in your cluster are the same, this
data can be obtained by dividing the cluster-level figures by the number of hosts. Resources being used
for virtualization purposes are not included. Only hosts that are connected, not in maintenance mode, and
that have no vSphere HA errors are considered.
The maximum number of slots that each host can support is then determined. To do this, the host’s CPU
resource amount is divided by the CPU component of the slot size and the result is rounded down. The
same calculation is made for the host's memory resource amount. These two numbers are compared and
the smaller number is the number of slots that the host can support.
vSphere Availability
VMware, Inc. 24